Ignition system



May 1, 1952 J. G. RUCKELSHAUS 3,032,683

IGNITION SYSTEM 3 Sheets-Sheet 1 Filed Jan. 6, 1959 May 1, 1962 J. G.RUcKELsHAUs 3,032,683

IGNITION SYSTEM 3 Sheets-Sheet 2 Filed Jan. 6, 1959 May 1, 1962 J. G.RUcKELsHAUs 3,032,683

IGNITION SYSTEM Filed Jan. 6, 1959 5 Sheets-Sheet 3 f 7j l /ff @9% f 2 la @f 5W #j United States Patent ili 3,032,683 Patented May I, i9623,032,683 IGNITION SYSTEM lohn G. Ruckelshans, 110 Pomeroy Road,Madison, NJ. Filed Jan. 6, 1959, Ser. No. 785,173 6 Claims. (el. sis-180) This invention relates to an ignition system utilized in internalcombustion engines and more particularly to a novel, low voltage systemfor distributing power to surface gap ignition plugs in a multi-cylinderengine.

Present ignition systems utilized in multi-cylinder internal combustionengines include a spark plug associated with each engine cylinder. Eachspark plug has a pair of spaced electrodes electrically insulated fromeach other. A high voltage is developed from a storage battery by meansof an electro-mechanical vibrator and stepup transformer and suchvoltage is applied across the electrodes of the individual spark plugsin proper ring sequence by a distributor having a rotating contactmaintained in timed relation to the motor speed. It is known that theconventional ignition system suffers' numerous practical disadvantagesin addition to the high voltage requirement such as, for example,deterioration of the distributor contacts, the generation of interferingradiofrequency waves, deterioration of the spark plug electrodes, andloss of efficiency due to the accumulation of carbon on the spark plugelectrodes.

In an ignition system having conventional spark plugs, a high voltage,of the order of 20,000 volts, is required to produce a hot spark acrossthe electrodes to thereby ignite the compressed `gasoline-air mixturewithin the engine cylinder. Although the voltage requirement is high,the magnitude of the current flowing across the electrode gap during thespark period is relatively low.

There has recently been developed a surface gap plug, or igniter, whichdiffers fundamentally from the conventional spark plug in that there isprovided between the electrodes a semi-conductor material having aninitial resistance of 30,000-500,000 ohms. When a voltage of 150-400volts is applied across the electrodes of a surface gap igniter theresistance of the semi-conductor material decreases to a very low valuepermitting a current of several hunderd amperes to ilow between ratherthan jump across the electrodes.

The advantages of the surface gap igniter are numerous as, for example,such igniter will operate in extreme moisture (even immersed in water),it provides a tremendously hot spark which promotes easier enginestarting at low temperature, permits the use of more economicalgasoline, and it is not adversely affected by the accumulation of carbondeposits on the electrodes, thereby resulting in a longer, uniformoperating life.

To date, the surface gap igniter has been employed only in singlecylinder engines, such as jet engines, where the ignition system isrequired only to start the engine. It has not been utilized inmulti-cylinder engines because of the impracticability of switching, ordistributing, a current in excess of 200 arnperes at voltages up to2,000 voltages without excessive arcing and disintegration of thedistributor contacts.

An object of this invention is the provision of an efficient, economicalsystem for the distribution of power to surface gap ignition plugs in aymulti-cylinder engine.

An object of this invention is the provision of a low voltage ignitionsystem for actuating a multi-cylinder engine, which system operates atrelatively low voltages, does not require an electro-mechanicalvibrator, does not include mechanical contact points, and produces aminimum of radio interference.

An object of this invention is the provision of a rotary gapdistributorv for sequentially distributing electrical energy to aplurality of surface gap igniters.

An object of this invention is the provision of a novel distributoradapted for converting a conventional distributor for use in an ignitionsystem utilizing surface gap igniters.

These and other objects and advantages will become apparent from thefollowing detailed description when taken with the accompanying drawingsillustrating several embodiments of the invention.

In the drawings wherein like reference characters denote like parts inthe several views:

FIGURE l is an elevation view of a surface gap igniter, with parts shownin cross-section;

FIGURE 2 is a schematic diagram of an ignition system made in accordancewith this invention;

FIGURE 3 is a diagram showing a transistor power supply for energizingthe ignition system;

FIGURE 4 is a fragmentary diagram showing a full wave rectifier forrectifying the output voltage of the high voltage transformer;

FIGURE 5 is a fragmentary diagram showing another embodiment of theinvention;

FIGURE 6 is an elevation view of my novel distributor with portions ofthe housing broken away and with parts shown in cross-section;

FIGURE 7 is a fragmentary, plan View, looking down into the distributorbase and showing the essential parts of a conventional distributor forautomatic spark advancement by means of conventional vacuum bellows; and

FIGURE 8 is essentially, a cross-sectional view taken along the line 8 8of FIGURE 7 and with the distributor top attached to the distributorbase, portions of the housings being broken away.

Referring to FIGURE l, the surface gap igniter, or spark plug, comprisesa metal shell I0 provided with a lower, threaded end 11 adapted to bethreaded into a suitable hole provided in the wall of an enginecylinder. The threaded end 11 constitutes the outer electrode which isgrounded to the engine and the other electrode cornprises anaxially-disposed, headed rod 12 that extends upwardly through aninsulator 13, which may be glass, ceramic, or etc. Extending along thegap between the electrodes 11 and 12, at the lower ends thereof, is asemiconductor material I4, which is fired -on to the lower end of theceramic and which, by reason of the concentric disposition of theelectrodes, takes the form of a washer. Intimate contact between thesemi-conductor material and the electrodes is desirable although notrequired for efficient ignition. The initial resistance of thesemi-conductor material, taken radially between the electrodes, may varyfrom 30,000 to 500,000 ohms and this resistance may increase or decreaseafter the igniter has been used, depending upon the atmosphere withinthe combustion chamber of the cylinder. With a voltage of between -400volts applied across the electrode-s 10 and 12 the resistance of thesemi-conductor material decreases tremendously, whereby a current havinga magnitude of hundreds of amperes flows along the surface of thesemiconductor material from the center electrode to the outer electrode,thereby producing a tremendously-hot spark to ignite the gasoline-airmixture within the combustion chamber. It is interesting to note thatthe igniter will lire at 150-400 volts, regardless of the compressionratio of the engine in which the igniter is used.

Surface gap igniters are well known, but such devices are generallyproduced with a flush surface between the electrodes and thesemi-conductor material. I prefer to construct the igniter so that theend of the inner electrode extends somewhat beyond the lower surface ofthe outer electrode whereby the semi-conductor material forms atruncated'cone, as specifically sho-wn in FIGURE l. 'In an igniter soconstructed, the inner electrode tip and the sem-i-conductor materialextends substantially into the gasoline-air mixture and I have found byactual tests such igniters provide instant and positive ignition at highengine speeds.

Reference is now made to FIGURE 2 which is a diagrammatic showing of mynovel ignition system as applied to a six (6) cylinder engine. Aconventional 6 or l2 volt storage battery l5 is connected to the primaryWinding 16 of a step-up transformer 17 through a vibrator or chopper 18,the battery being grounded in accordance with conventional practice.'The vibrator may be of any standard construction and its function is toapply the battery voltage across the transformer winding in a series ofpulses so as to produce in the secondary winding 19 aperiodically-varying voltage of increased level, as is well known. Inthis particular application, I prefer to make the transformer turnsratio such that the voltage developed in the secondary winding isapproximately 2,000 volts. The output voltage of the transformer isapplied across a capacitor 20, through a current-limiting resistor 21and a rectier 22. With the rectifier conducting in the indicateddirection, the capacitor will become charged as indicated by thepolarity marking during each half cycle of the transformer outputvoltage.

'Ihe reference numeral 23 identities the distributor comprising a sealedchamber with six (6) fixed electro-des or points, 24-29, extendingtherethrough and a rotatable electrode 30. The rotatable electrode issecured to the distributor shaft whereby such electrode rotatesthroughout 3 60 degrees in precise, timed relation with the enginespeed. The construction of the distributor will be described in detailhereinbelow, with specific reference to FIGURE 6. Suffice to say', atthis point, that the rotatable electro'de 30 has a pointed tip spacedfrom the pointed, inner tips of the xed electrodes thereby forming whatmay be termed a rotary gap.

In FIGURE 2, there are shown six (6) surface gap igniters 31-36 of thegeneral construction shown in FIG- URE l. When installed in -a sixcylinder engine, the outer electrodes of the ign-iters are grounded andthere exists a resistance of 30,000 to 500,000 ohms between the innerand outer electrodes of each igniter as represented in the drawing bythe resistances SL42. Because of this resistance, an air gap is requiredbetween the igniter and the capacitor 20, so that the latter can beinstantly and fully charged. Assuming a fully charged capacitor, it Willbe apparent that as the distance between the distributor rotatableelectrode 30 and, for example, the ixed electrode 24, is reduced to aminimum, pre-set air gap, the Voltage existing across the capacitor willionize the gap between the aligned distributor electrodes and thecapacitor will discharge through a series circuit consisting of such airgap, the igniter electrodes and the ground return to the other side ofthe capacitor. If the frequency of the rectified voltage applied acrossthe capacitor exceeds the time during which the rotatable distributorelectrode 30 moves between adjacent fixed electrodes, the capacitor willbecome substantially fully charged during the time interval that therotatable electrode rotates from one to the next xed electrode. Byapplying approximately 2,000 volts across the capacitor during thecharging period, the voltage level to which the capacitor becornescharged, during even minute charging periods, will at least exceed theminimum voltage required to ionize the gap between aligned distributorelectrodes and result in a voltage applied across the igniter electrodesto cause positive ring. Consequently, upon continuous rotation of therotatable electrode 30, current will flow from the rotatable electrodesuccessively to each of the ixed electrodes and through and over thesurface of the semi-conductor material between the electrodes of theassociated igniter. Those skilled in this art will understand that theindividual igniters are connected to the fixed contacts of thedistributor so as to obtain the correct tiring order. Also, although Ihave shown, in FIG- URB 2, an ignition system for a six cylinder engine,it is apparent that the system may be used on an engine having anynumber of cylinders in which instance the number of xed contacts equallyspaced in the distributor will correspond to the number of igniters andthe frequency of the voltage applied to the capacitor will be selectedto assure full charging of the capacitor at maximum engine speed.

The energy discharged by the capacitor 20 is very high for ignition use,being of the order of 0.2 joule and running as high as 5.0 joules. Thecurrent during the discharge period can be as high as a few thousandamperes. This current, at 2,000 volts, produces a very serious switchingproblem, especially in conned space, as in the cap of a distributor, andhas been the main reason Why surface gap igniters heretofore have notbeen adapted for use in multi-cylinder engines. I have overcome thisproblem by providing a rotatable gap disposed within a sealed chamber soas to exclude oxygen and other gases which promote and enhance theburning of electrical contacts breaking heavy currents at high voltages.

There is still another reason Why the switching problem is not asserious as in prior art circuits. Conductor and other conductors coupledto the capacitor 20 and ground include some small resistance values andsome inductance. When the capacitor first discharges through the gap andignitor, the current builds up to a maximum value and then is reduced toa negligible amount as the capacitor is fully discharged. Because of theinductance in the Wiring, the current is made slightly oscillatory andthe current is reversed by a small amount, charging the capacitor 20 inan opposite direction. The resistance in the conductors, gap, andigniter reduce the oscillatory voltage to a very small amount, the netresult being a steep reduction in igniter current to zero before thedistributor arm leaves the stator electrode. This action reduces sparkdeterioration and permits higher engine speeds.

FIGURE 3 illustrates a transistor inverter, or power supply forenergizing my ignition system. The two transistors 44, 45 operate asswitches, one being on while the other is o. Assume that thetransistor-44 is conducting and the transistor 45 is blocked. Thiseffectively connects the battery 15 across the upper half of thecenter-tapped primary winding e7 of the transformer 48, thereby inducinga voltage in the secondary winding 49 and in the auxiliary winding 50.At the instant that transistor 44 starts to conduct, the voltages in thetransformer windings Will assume a maximum voltage level. This conditionwill continue to exist until the core of the saturable reactor 51 beginsto saturate at which time the rate of change of flux will decrease.During the same time interval, the induced voltages first decrease invalue and then become Zero. This decreases and then removes the basedrive to transistor 44. The current now begins to decrease and causesthe transformer flux to build up in the opposite direction whereby avoltage of opposite polarity is induced in the transformer windings andthe transistor 45 begins to conduct. The cycle is then repeated. Thevoltage output of the inverter will be a square wave whose frequency andamplitude are determined by the number of turns on the primary windingof the transformer, the voltage of the battery, and the saturation fluxof the reactor. The resistors 52 and 53 implement the starting ofoscillation of the circuit by biasing the transistors out of thenon-linear, low current region, and the R-L network, consisting of theauxiliary winding 50, inductance 51 and the variable resistor 54,determines the oscillation frequency of the inverter circuit. I preferto design the inverter components so that the voltage appearing acrossthe transformer secondary winding 49 will have a frequency of about 800cycles per second and a magnitude of 2,000 volts. I have found that avoltage of this level and frequency results in sufficient charging ofthe capacitor 20, when the rotatable electrode of the distributor 23rotates at maximum engine speeds normally encountered in eight cylinderengines, to assure proper firing of the igniters. Toward this samepurpose, the alternating voltage of the highvoltage transformer may befully rectified as shown in the fragmentary circuit diagram of FIGURE 4.In such arrangement, the charging voltage pulses applied to thecapacitor 20 will be at a rate twice that of the halfwave systems shownin FIGURES l and 2, since both positive and negative waves are rectifiedby .the rectifier 59.

FIGURE 5 illustrates a modification of the ignition system. In thiscase, the rotatable contact 57 of the distributor 23 has a tip whichactually engages the tips of the fixed electrodes, thereby clsoing theelectrical circuit between the secondary winding 49 of the transformer48 and one of the igniters 31', 32', 33', etc. The igniters are herepresented in .terms of electrical equiv- -alents, namely, a gap formedbetween the inner and outer electrodes with the resistances 37', 38", 39representing the shunting resistance across the gap arising by reason ofthe semi-conductor material. Separate capacitors 20a, 20b, 20c, areassociated with each igniter as are separate fixed, gaps 58a, 58b, 58C.As shown in the drawing, the rotatable contact 57, of the distributor,is in contact with the fixed Contact 24e, thereby completing theelectrical circuit between the transformer winding 49 and the capacitor20c through the current-limiting resistor 21 and the rectifier 22. Thischarges the capaci- 4tor 20c. When the rotatable contact 57 moves out ofcontact with the fixed contact 24C, the capcaitor 20c discharges throughthe gap 58C and through the igniter. This cycle is repeated as therotatable distributor contact is brought sequentially into and out ofengagement with the fixed contacts, resulting in a correspondingsequential charging of the individual capacitors 20a, 2Gb, 20c and Ithedischarging thereof through the associated igniter and gap. Since theswitching is done ahead of the capacitor, the contacts carry only asmall current which, together with the sealed casing 29', lresults in along contact life. Further, by making the rotatable and fixed contactsof a radio active material, the cooperating contacts need not actuallycome into physical contact, in which case the distributor becomes arotary gap similar to the one in the FIGURE 2 embodiment.

FIGURE 6 illustrates the construction of the rotary gap distributor usedin the ignition systems shown in FIG- URES 2, 3 and 4. Although suchdistributor may include a housing of any appropriate design, the housingshown in the drawing is that of a conventional distributor consisting ofthe base 60 and cap 61. This is intended to show that my noveldistributor is adapted for quick and easy substitution for the presentdistributor on an engine to thereby adapt the engine for operation withsurface gap igniters. In fact, my distributor cap is readily mounted onthe base of a conventional distributor installed on an engine withoutrequiring adjustment of the timing. Toward this end, the contact andbreaker points of the conventional distributor merely are removed.

Extending centrally through the distributor base 60 is a conventionaldistributor shaft 62 provided with a fiat portion 63 which serves forremovably coupling my distributor to such shaft while maintaining aproper timing relation. The open end of the distributor cap 61 (whichmay be molded of a clear plastic, as shown), is closed by means of ametal plate 63 that is secured in position by a plurality ofcircumferentially-spaced screws 64. It is preferable that the interiorof the cap be sealed, the washers 65, 66 being provided for thispurpose. To maintain the sealed character of the distributor, a VanderGraff shaft seal 67 is utilized. Such seal comprises a metal housing 68(which, in this instance, is welded centrally to the plate 63) and thewashers 69, 70, 71 tightly igniters, associated with a particularengine.

encircling the shaft 72. It will be noted that the shaft 72 is providedwith reversely-threaded portions 73, 7 4 so that rotation of the shaft72 will tend to throw grease (which fills the chamber within the bushing68) toward the central washer 70 and away from the end-sealing washers69, 71, thereby promoting the maintenance of a good seal between theshaft 72 and the interior of the distributor cap 61. The grease may beinserted into the seal 67 through the opening provided upon removal ofthe screw 75.

In order to reduce radio-frequency interference to a minimum, theplastic distributor cap 61 is disposed within a metal shell 77, whichshell has an inwardly-directed flange 78 and ay reduced-diameter,extended portion 79. The latter is provided with an undercut ridgewhereby the metal shell 77 may be removably secured to the distributorbase 60 by conventional latching clamps 80. The fiange 78 provides aconvenient means for securing the cap 61 to the shell 77 as by aplurality of circumferentiallyspaced screws 81. It will be noted thatthe outer end of the shaft 72 is provided with a diametric hole throughwhich is inserted a drive pin 82. A coupling collar 83 has a diametricslot formed therein for accommodating the pin 82 and the forward end ofthe collar is provided with a bore such that the coupling collar can beinserted over the end of the distributor shaft 62. It will be apparentthat such arrangement affords a means for quick, positive and accuratecoupling and uncoupling of the shafts 62 and 72. Thus, to remove themetal housing 77, which carries the cap 61, from the base 60, it is onlynecessary to unsnap the latching clamps and draw the housing 77 awayfrom the base, the latter generally being firmly secured to the engine.Conversely, to install the distributor in operative position, it is onlynecessary properly to align the bore in the coupling collar 83, slidesame over the shaft 62 and close the latching clamps 80.

The 'inner end of the shaft 72 has secured thereto an insulator bushing85, as by the screws 86. The rotatable electrode 87 extends radiallyfrom a contact plate 88, being secured thereto by a set screw 89, andthe Contact plate is, in turn, firmly secured to the insulator bushing85 by suitable screws 90. It may here be pointed out that the electrode87 is preferably made of tungsten and the contact plate 88 is made ofbrass or copper and has a substantial mass so that it acts as a heatsink to keep the electrode relatively cool.

A conventional distributor cap, such as the cap 61, shown in FIGURE 6,includes integral, upstanding bosses or insulator bushings which serveto position individual terminal rods. These terminal rods, which may bemolded directly into the plastic cap or otherwise firmly secured inposition, have individual leads soldered thereto, which leads preferablyare of the shielded cable type and pass outside of the metal shell 77through a suitable opening. The center terminal rod 91 has an axial boreformed in the inner end for the accommodation of a helical spring 93 andthe inner end of a carbon brush 94. Thus, it is apparent that a goodelectrical circuit is established between the rotatable electrode 87 andthe terminal rod 91 through the medium of the contact plate 88 and thespring-biased brush 94. Circuitwise, the lead 95, secured to the centerterminal rod 91, is connected to the positive side of the capacitor, seeparticularly FIGURE 3. Each of the other leads (connected to the otherterminal rods) individually are connected to the center electrode of theassociated igniter.

Although only four terminal rods, namely, those identified by thenumerals 96-99, are visible in FIGURE 6 in addition to the center rod91, those skilled in this art will understand that the number of suchadditional terminal rods corresponds to the number of spark plugs, orThe fixed electrodes of the distributor are carried by individual screws100 which are threaded through aligned, threaded holes formed in theside wall of the cap 61 and the associated terminal rod. Force-fittedinto an axial bore formed in each screw is a pointed electrode 101, thetips of such fixed electrodes lying in the plane generated by therotatable tip 87 upon rotation of the distributor shaft 62. Access toeach of the screws 100, as by means of a screwdriver, is obtained uponremoval of the threaded plugs 102 whereby the spacing between the tip ofthe rotatable electrode and the tips of the fixed electrodes may beindividually adjusted to a precise distance. It is here pointed out thatthe tips 87 and 101 preferably are made of tungsten and are pointed, theformer promoting long, operating life and the latter providing veryaccurate timing inasmuch as the gap distance may be adjusted, with dueconsideration given to the discharge voltage of the capacitor, so thatthe capacitor will discharge when the rotatable tip 87 is substantiallyin precise alignment with a fixed electrode point.

The open end of the metal, outer shell 77 is closed by a metal plate 103secured by screws 105. Thus, the entire distributor is enclosed within ametal housing which, together with the use of shielded cable leads,practically completely eliminates radio interference. The sealedcharacter of the distributor chamber makes it possible to evacuate suchchamber and/ or till same with an inert gas, all directed towardpromoting long, trouble-free operation.

A conventional ignition system using convetnional spark plugs generallyincludes an automatic spark advance arrangement to promote quicker andeasier engine starting. Briefly, such an arrangement utlizes avacuum-operated bellows mechanically coupled to a plate carried in thebase of the distributor, which plate is adapted for limited rotarymovement and carries the distributor points. In tests which I haveconducted with my low voltage ignition system installed on a six (6)cylinder marine engine, I have found no need for a spark-advancefunction. However, by making a slight modification in the constructionof the distributor cap, my distributor is made adaptable forinstallation on a conventional distributor base provided with theautomatic, spark-advance mechanism. FIGURE 8 illustrates the modifiedform of my'distributor, but reference is first made to FIGURE 7 `FIGURE7 is an elevational view of a conventional distributor base 6i) with theconventional breaker points removed. A rocker plate 110 is mounted forlimited rotary movement as defined by the arcuate slots 111 throughwhich pass the locating and positioning screws 112. A iiat rod 113 ismechanically coupled to the plate 110 by means of a pin 113 that issecured to the plate and passes through a clearance hole provided in therod. The other end of the rod 113 is attached to the vacuum-operatedbellows disposed within the housing 114 that is secured to the base 60.It will be apparent that as the bellows expand and contract the plate110 will rotate ink a clockwise and counter-clockwise direction,respectively. Secured to the plate 110, and extending upwardlytherefrom, is a pin 115. This pin normally serves as one means forrotatably supporting the conventional breaker points. For my purpose,the conventional breaker points are removed and the pin 115 is utilizedfor coupling the rocker plate 110 to the cap of my distributor as willnew be described with speciiic reference to FIG- URE 8.

As shown in FIGURE 8, the rocker plate 110 is supported by a ange 116extending inwardly from the side Wall of the distributor base 60. Thelocating screws 112, which pass through the arcuate clearance holes 111formed in the plate, are threaded into suitable holes provided in theange 116. The coupling pin 115, which is secured to the plate 110,extends into an axial bore formed in the aligned bushing 117 secured tothe plate 63 which closes the end of the distributor cap 61. The sealedcharacter of the cap is maintained by the screws 64 and the washers 65and 66. In this modified construction, however, the screws 81, whichsecure the cap 1 to the outer shell 77, pass through enlarged holesformed in the ange '78, thereby permitting a slight rotation of theentire cap 61 in correspondence with rotation of the plate through thecoupling means comprising the pin and the lbushing 117. Inasmuch as thetixed electrodes are carried by the cap 61, rotation of the cap willchange the angular position at which the center rotatable electrodecornes into precise alignment with the individual, fixed electrodes,thereby changing the tiring point with respect to the angulardisposition of the shaft 62.

From the above description, it is apparent that I have provided a lowvoltage ignition system making it possible to use surface gap ignitersin a multi-cylinder engine. In the preferred form, the system does notrequire a switching function involving the opening and closing of anelectrical circuit by the engagement and disengagement of breaker points(such as is required in conventional high voltage ignition systems)thereby promoting dependable and positive ignition with a minimum ofmaintenance. By using tungsten electrodes disposed within a sealedchamber the operating life of the electrodes is increased substantially.A further increase in the electrode life may be obtained by filling thesealed distributor chamber with dry air or an inert gas. In order toreduce the voltage necessary to ionize the gap between alignedelectrodes, the rotary and xed electrodes may be made of a radio activematerial. Of equal importance is the fact that my rotary gap distributorcan be installed on the base of a conventional distributor having aspark advance mechanism of the vacuum-operated and/or centrifugal type,without requiring alterations, without need of special tools, andwithout the necessity of retiming.

Having now described my invention in detail, in accordance with thepatent statutes of the United States, those skilled in this art will ndno difficulty in making changes and modifications to meet specificoperating conditions or requirements. It is intended that such changesand modications shall fall within the scope and spirit of the inventionas recited in the appended claims.

I claim:

l. A low Voltage high current ignition system for an engine having aplurality of surface gap igniters comprising a rotatable gap distributorconsisting of a sealed chamber, a rotatable electrode disposed withinthe chamber and iixed electrodes each having an end disposed within thechamber and radially-spaced from an end of the rotatable electrode;leads individually connecting each fixed electrode to the centerelectrode of an associated igniter; a capacitor having one sideconnected to the said rotatable electrode and the other side connectedto the outer electrode of each igniter; a D.C. voltage source; atransformer having a secondary winding connected to the capacitorthrough a rectifier, a center-tapped primary winding and an auxiliarywinding; and a push-pull oscillator energized by the said voltage sourceand supplying energy alternately to the two portions of the saidcenter-tapped primary winding, said oscillator including an iron coreinductor connected across the said auxiliary winding and having a centertap connected to the center tap of said primary winding.

2. The invention as recited in claim l, wherein the oscillator includesa pair of transistors each having a base, an emitter and a collectorwith the emitters connected to opposite ends of the said center-tappedprimary winding, and the bases connected to opposite ends of the saidinductor.

3. A low voltage, high current ignition system for an engine having aplurality of surface gap igniters comprising a rotary gap distributorconsisting of a sealed chamber, a rotatable electrode disposed withinthe chamber and tixed electrodes each having an end disposed within thechamber and radially-spaced from an end of the rotatable electrode;leads connecting each fixed electrode to the center electrode of anassociated igniter; a capacitor having one side connected to saidrotatable electrode and the other side connected to the outer electrodeof each igniter; a D.C. voltage source; a transformer having a secondaryWinding, a center-tapped primary Winding and an auxiliary winding;circuit elements applying the voltage developed in the transformersecondary Winding to the capacitor through a rectifier; a pair oftransistors each having a base, an emitter and a collector; meansconnecting the said center-tapped primary Winding between the transistorcollectors; an iron core inductor having a centertapped winding; meansconnecting the ends of the inductor Winding between the transistor basesand across the transformer auxiliary winding; means connecting thetransistor emitters to the positive side of the D.C. voltage source; apair of resistors connected in series across the said voltage source;and a lead connecting the center tap on the inductor winding to thecommon point of said resistors.

4. The invention as recited in claim 3 including a third resistorconnected between ends of the said auxiliary Winding and the inductorWinding.

5. The invention as recited in claim 4, wherein the distributor isenclosed Within a metal housing and the leads extending therefrom areshielded cables.

6. An ignition system for engines having a plurality of surface gapigniters to be red sequentially, said systern comprising a storagecapacitor, a source of voltage connected across the capacitor forcharging it, a rotary gap distributor including a rotatable electrodeand a plurality of spaced, fixed electrodes radially spaced from an endofthe rotatable electrode, conductors individually connecting each fixedelectrode to the center of an associated igniter, and coupling meansconnecting the positive side of said capacitor to the rotatableelectrode and the negative side of the capacitor to the outer electrodeof each igniter, said storage capacitor forming a part of a resonantcircuit which includes the inductance of the coupling conductors and arectifier, said resonant circuit adapted to reduce the current throughthe igniters to a minimum value before the rotatable electrode leaveseach of said fixed electrodes.

References Cited in the ile of this patent UNITED STATES PATENTS2,354,302 Carlson July 25, 1944 2,544,477 West Mar. 6, 1951 2,587,780Smits Mar. 4, 1952 2,589,164 Tognola Mar. l1, 1952 2,590,168 Felici Mar.25, 1952 2,837,698 Segall June 3, 1958 2,852,730 Magnuski Sept. 16, 19582,883,539 Bruck et al Apr. 2l, 1959 2,916,704 Morey Dec. 8, 1959 FOREIGNPATENTS 724,016 Great Britain Feb. 16, 1955

